Conventional 35mm film cartridges are normally sold with a portion of the film leader projecting from the exit slot of the cartridge. This allows the camera user to grasp and pull the film for loading in the camera and at the same time provides a visual indication to the camera user that the film in the cartridge is unexposed. Upon rewind, the film is rewound completely into the cartridge and the absence of the protruding leader indicates that the film has been exposed and prevents reuse of the film in a camera thus inherently providing protection against double exposure of the film. Recently, camera and film cartridge designs have been proposed in which the film is totally enclosed in the cartridge when sold. To load the film, the cartridge is inserted and the drive motor operates to thrust the film out of the cartridge to the film take-up spool. Upon rewind, the film is drawn entirely into the cartridge. As a consequence, there is no visual indication to distinguish between an exposed and an unexposed film roll and, thus, numerous camera and cartridge designs have been proposed to provide protection against re-use and double exposure of the film.
It is known, for example, to provide cartridges with mechanical features that cooperate with feelers in the camera that prevent insertion of cartridges into the camera when the film has previously been exposed. In many cases these mechanical features also provide a visual indication of the exposed condition of the film. A representative example of an arrangement providing both visible indication and mechanical lockout means is found in commonly assigned U.S. Pat. No. 5,047,794. U.S. Pat. No. 5,115,268 discloses a mechanical slide on the film cartridge is movable by a cam arrangement upon insertion into the camera to cover the letters UN in the word UNEXPOSED printed on the end of the cartridge to provide a visible indication of an exposed condition of the film in the cartridge. In commonly assigned U.S. Pat. Nos. 5,032,854 and 5,030,978, a radial bar coded disc on the end of a film cartridge is sensed by an opto-sensor in the camera to position the film spool upon conclusion of rewind at a selected one of plural visual indicators that indicate the exposure condition of film in the camera.
Such arrangements however, require special cartridge designs that add to the cost and complexity of cartridge manufacture. In the case of cartridges with just visual indicators, it is possible to ignore the indicators and load the film into the camera thereby creating a possibility of double exposure of the film.
It is therefore an object of the invention to provide a simple, inexpensive cartridge and camera configuration that provides both a visual indication of the exposure condition of photographic film that also provides the capability of automatically preventing loading of exposed film into the camera thereby avoiding the possibility of double exposing the film in the camera.